The present invention is directed to oilfield tools and assemblies. Specifically, the invention relates to an apparatus and method for supporting and actuating a concentric casing string during drilling operations.
It is often useful to utilize a second string of casing, tubing, or dill pipe inside the production casing when drilling for oil, gas, or water. Frequently, the inner string of concentric casing is supported from the surface and the drill string is inserted inside the inner string of casing. The drill string may then be operated independently of the inner string of casing. Additionally, it is often desirable to be able to vertically actuate the inner casing so that a tool attached to the lower end of the inner casing may be operated. An apparatus that supports the inner casing string from the surface and is able to actuate the inner casing string along its vertical axis is known as a casing jack.
The prior art has frequently addressed the subject of supporting an inner string of casing or tubing within the well bore. U.S. Pat. No. 6,019,175 (the ""175 patent) discloses an apparatus and method for hanging a tubing string within a well bore and permitting vertical displacement of the tubing string without removal of the wellhead. However, the ""175 patent is limited in that it does not disclose a method or apparatus for vertically actuating the tubing string to operate down hole tools.
U.S. Pat. No. 6,009,941 (the ""941 patent) discloses an apparatus for supporting and vertically displacing a downhole tool or a tubing string. However, the ""941 patent is limited in that it discloses a complicated apparatus that is difficult to install and operate in the field. A need exist beyond the ""941 patent for an apparatus and method of supporting and vertically displacing a tubing or casing string that is simple to install and operate.
What is needed beyond the prior art is an apparatus and method for supporting tubing or casing that is also capable of vertically actuating the tubing or casing during drilling operations. Additionally, a need exists beyond the prior art for a casing jack that is simple to install and can be operated independently of a drill string.
The present invention, which meets the needs stated above, is a concentric casing jack having a casing supporter and actuator that uses hydraulic fluid to vertically raise and lower an inner concentric string of casing in a well. The concentric casing jack is connected to a string of casing and can operate down-hole tools attached to the lower end of the casing by actuating the casing. The casing jack is supported at the surface by the wellhead and can be incorporated into a series of drilling spools and blowout preventer valves that are commonly utilized during drilling operations. The concentric casing jack consists of a housing and a piston whose internal diameter is similar in size to the concentric casing. The similar sizing allows drill bits and bottom hole assemblies to pass through the hollow center of the casing jack and the attached string of casing. The piston is equipped with external seals to hold hydraulic pressure between the hollow piston and the body of the jack. The lower shaft of the piston extends through the base of the casing jack housing where the lower shaft is threaded onto the concentric string of casing in the well bore. The upper shaft of the piston extends above the top of the casing jack housing where it connects to the surface drilling equipment. The casing jack is equipped with two hydraulicaly retractable support plates that fit into recessed areas of the piston and support the weight of the casing and piston after the piston is in its raised position. The casing jack also contains an internal shoulder to support the piston and the casing when the piston is in the lowered position.